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Benthic Marine Algae of Rotuma Island
Rotuman Distribution
Common at most sites. Representative material: Kelega (K2/ USP 616).
Habitat and Remarks
On the exposed outer reef, where it occurs as more or less eroded concretions attached to
the coral rubble.
Gigartinales
Gracilariaceae
Gracilaria Greville 1830: 121
Gracilaria sp. aff. G. textorii (Suringar) De Toni 1895: 27; Xia and Yamamoto 1985: 69,
figs 24-31; Millar and Kraft 1993: 28.
Thallus foliose, consisting of irregularly dichotomous blades with rounded apices and
smooth margins. Medullary cells ovate to ovoid, 80-125 pm in diameter; cortex distromatic,
the outermost layer of pyriform to spherical cells 8-12 pm in diameter, the inner layer of
ovate to spherical cells 30-50 pm in diameter. Plants sterile.
Rotuman Distribution
Maka Bay (MAK20/ USP 614).
Habitat and Remarks
Growing abundantly within the seagrass beds in Maka Bay, in association with
Sargassum polycystum and Enteromorpha jlexuosa. Owing to a lack of fertile material, this
species of Gracilaria cannot be definitively identified. However, from its habit and internal
structure it most closely resembles G. textorii (Suringar) De Toni.
Hypneaceae
Hypnea Lamouroux 18 13: 13 1
Hypnea nidulans Setchell 1924: 161, fig. 30 (type locality: Tutuila Island, American
Samoa); Weber-van Bosse 1928: 454, fig. 192; Okamura 1931: 114; Tanaka 1941: 246, figs
18, 19; Dawson 1954: 438, fig. 46e-g; 1957: 115; Tsuda 1964: 9; Jaasund 1976: 97, fig. 197;
Tsuda and Wray 1977: 108; Lewis 1984: 35; Payri and Meinesz 1985a: 512; Lewis and
Norris 1987: 20; Silva et al. 1987: 50.
Hypnea nidulans is included within H. pannosa J. Agardh (1847: 14) by the following
authors: Womersley and Bailey (1970: 319); Kasahara (1985: 62); Tsuda (1991: 54); Price
and Scott (1992: 38), but both species are recognised by Silva et al. (1987: 50).
(Fig. 136)
Thallus purple-pink, up to 2 cm high, with mostly terete axes up to 1 mm broad.
Branching irregular, with arcuate tendency for the axis and branches. Branches not
constricted at the base, terminating in sharply acute apices. Medulla up to 740 pm in
diameter, consisting of a central axial cell giving way radially to medullary cells up to 200
p,m in diameter. Lenticular thickenings present in some medullary cells. Inner cortical cells
23-30 ym in diameter; pigmented epidermal cells 8-9 pm in diameter. Apical cell single,
prominent, up to 10 p,m in diameter.